Conventionally, there exists a contactless power receiving apparatus including: a resonance element adapted to receive supply of alternating-current power in a contactless fashion by resonance from a resonance element of a power supplying source; an excitation element adapted to receive supply of the alternating-current power by electromagnetic induction from the resonance element; a rectification circuit adapted to generate direct-current power from the alternating-current power from the excitation element and output the direct-current power; and a changeover circuit adapted to change over the alternating-current power to the rectification circuit between a supply state and a non-supply state (see Patent Document 1, for example).
Such a conventional contactless power receiving apparatus (power receiver) does not take into consideration efficiency of electric power reception when the resonance element receives the electric power transmitted to the power receiver. If the efficiency of electric power reception can be adjusted, it is possible to transmit electric power efficiently between the power transmitter and the power receiver.